What Must a Woman Cover from Another Woman, Such as Her Sister - Jurisprudential Answers - Miscellaneous Issues, Vol 1

Ahmed al-Hasan Response:

Regarding what a woman must cover from another woman, the obligation is indicated in God's words, 'Tell the believing women to lower their gaze and guard their private parts.' This concerns looking: a woman may not look at another woman's private parts, and a woman must guard and cover her own private parts from another woman's gaze. This is what is obligatory.